@Sommersang I am in favor of an embedded repeat for that reasons, but would settle for an meta repeat if the lore was to contrived or awkward ...

So, we have as requirements:- cycle of worlds- parallel worlds- different maps- different rules - many biomes in a small area

We might build some lore around the existing magicalness of the substance and biome packing...Just some thougths:- the valley got created by an erruption, that brought the substance to the surface and created a network of chasms- the meteors are in fact volcanic ejecta bombs from nearby erruptions, pigments might be created by geysers, steamvents, ...- the substance corrupts and embues sentinent beings with special powers- the substance corrupts and empowers the nature and the ground itself with special powers: regions might be tuned to certain effects same as the sentinent beings. This causes the different biomes and different rules...- the regions of the valley are unstable - existing areas might decay or new areas form quickly. The mist that removes imortability also causes quick decay of the land.- the glass like outermost walls of the chasm are mostly stable - earthquakes might shatter elevators and tunnels

To communicate those mechanisms in game, some continuous changes in the worldmap would help to tell the story - a biome coming alive over the course of the world and another biome decaying would anchor that story in the world visible to the players. Maybe we could gradually change the terrain texture, change the grass textures and size and replace some assets on a map sector? Or just open/close passages to sectors?More events that fit and tell the lore would also help...

Some of the AoE Skill FX could actually double as active substance in forming or decaying sectors. It would give a nice look and make them dangerous. In decaying sectors buildings should get ruined, in fresh sectors there could be an initial, non respawning population of revenants and some freely accessible resources...

Maybe the valley has a fairyland-like concept of space - see Stardust, Annihilation, Ludd in the Mist, ...The border/veil might ebb and flow, open up and close down sectors, inject or remove connecting sectors...Walls, shortcuts (wormholes) may appear and disappear - tap into skillfx for walls, shields, teleports, etc.